Only call custom tooltips when elements have changed. But be sure to call update internally any time that tooltips need to be redrawn.

samples/line-customTooltips.html

@@ -42,10 +42,11 @@
     <canvas id="chart1" width="300" height="100" />
   </div>
   <script>
+    window.count = 0;
     Chart.defaults.global.pointHitDetectionRadius = 1;
     var customTooltips = function(tooltip) {
 
-      console.log(tooltip);
+      console.log(window.count++, tooltip);
 
       // Tooltip Element
       var tooltipEl = $('#chartjs-tooltip');

src/core/core.controller.js

@@ -459,6 +459,7 @@
 				// The usual updates
 				this.tooltip.initialize();
 				this.tooltip._active = this.tooltipActive;
+				this.tooltip.update();
 			}
 
 			// Hover animations
@@ -484,11 +485,12 @@
 					(this.lastTooltipActive.length !== this.tooltipActive.length) ||
 					changed) {
 
-					if (this.options.tooltips.enabled || this.options.tooltips.custom) {
-						this.tooltip.update();
-					}
 					this.stop();
 
+					if (this.options.tooltips.enabled || this.options.tooltips.custom) {
+						this.tooltip.update(true);
+					}
+
 					// We only need to render at this point. Updating will cause scales to be recomputed generating flicker & using more
 					// memory than necessary.
 					this.render(this.options.hover.animationDuration, true);

src/core/core.tooltip.js

@@ -193,7 +193,7 @@
 			return lines;
 		},
 
-		update: function() {
+		update: function(changed) {
 
 			var ctx = this._chart.ctx;
 
@@ -262,7 +262,7 @@
 				this._model.opacity = 0;
 			}
 
-			if (this._options.tooltips.custom) {
+			if (changed && this._options.tooltips.custom) {
 				this._options.tooltips.custom.call(this, this._model);
 			}
 
@@ -270,6 +270,7 @@
 		},
 		draw: function() {
 
+
 			var ctx = this._chart.ctx;
 			var vm = this._view;